EP0103917A1 - FM-Stereoempfänger - Google Patents

FM-Stereoempfänger Download PDF

Info

Publication number
EP0103917A1
EP0103917A1 EP83201127A EP83201127A EP0103917A1 EP 0103917 A1 EP0103917 A1 EP 0103917A1 EP 83201127 A EP83201127 A EP 83201127A EP 83201127 A EP83201127 A EP 83201127A EP 0103917 A1 EP0103917 A1 EP 0103917A1
Authority
EP
European Patent Office
Prior art keywords
detector
stereo
input
circuit
mono
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
EP83201127A
Other languages
English (en)
French (fr)
Other versions
EP0103917B1 (de
Inventor
Theodor Ignatius Eduard Kamalski
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Koninklijke Philips NV
Original Assignee
Philips Gloeilampenfabrieken NV
Koninklijke Philips Electronics NV
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Philips Gloeilampenfabrieken NV, Koninklijke Philips Electronics NV filed Critical Philips Gloeilampenfabrieken NV
Publication of EP0103917A1 publication Critical patent/EP0103917A1/de
Application granted granted Critical
Publication of EP0103917B1 publication Critical patent/EP0103917B1/de
Expired legal-status Critical Current

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
    • H04B1/06—Receivers
    • H04B1/10—Means associated with receiver for limiting or suppressing noise or interference
    • H04B1/1081—Reduction of multipath noise
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
    • H04B1/06—Receivers
    • H04B1/16—Circuits
    • H04B1/1646—Circuits adapted for the reception of stereophonic signals
    • H04B1/1661—Reduction of noise by manipulation of the baseband composite stereophonic signal or the decoded left and right channels
    • H04B1/1669—Reduction of noise by manipulation of the baseband composite stereophonic signal or the decoded left and right channels of the demodulated composite stereo signal

Definitions

  • the invention relates to an FM-receiver comprising an aerial input having connected thereto, in succession, an RF input stage, an IF portion, an FM-detector and a stereo decoder and also comprising a control signal generating circuit and a mono-stereo control circuit connected thereto, the control signal generating circuit comprising a multipath reception detector and being connected to the IF portion via a level detector, the multipath reception detector comprising an amplitude detector connected to the level detector via a bandpass filter.
  • the prior art FM-receiver comprises a mono-stereo switching circuit which at a low field strength and/or a high degree of multipath reception effects a mono reproduction and at a high field strength and a low degree of multipath reception effects a stereo reproduction.
  • the audible noise produced by poor signal reception is thereby reduced at the cost of a spatial reproduction.
  • the multipath reception is measured by amplitude detection of the output signal of the level detector within the passband of said bandpass filter, the level detector being connected to the IF- portion.
  • This passband may either be wide-banded (extending from some KHz to approximately 100 KHz) or narrow- banded around 19 KHz or 57 KHz.
  • the field strength is measured by an integration of the output signal of the said level detector.
  • the control signal for the mono-stereo switching circuit is obtained by subtracting the output signals of the multipath receptor and the field strength detector from each other, after a mutual amplitude match.
  • Pulse-shaped, artificial interference caused, for example, by electric ignition of internal combustion engines may however produce noise components which pass said bandpass filter and are included in the measurement of the multipath reception.
  • the control signal for the mono-stereo switching circuit of the prior art FM receiver is consequently partly determined by the said noise pulses.
  • an FM-reoeiver of the type described in the opening paragraph is characterized in that in case the FM-receiver comprises a noise pulse suppression circuit arranged between the FM-detector and the stereo decoder for keeping the amplitude of the stereo multiplex signal constant during the occurrence of noise pulses, the bandpass filter has a lower 3 dB cut-off frequency of the order of magnitude of 1 KHz and an upper 3 dB cut-off frequency of not more than of the order of magnitude of 10 KHz.
  • noise pulses in the signal path as well as in the control path are eliminated.
  • the elimination of noise pulses in the signal path is effected by means of said noise pulse suppression circuit which is known per se from, for example, German Patent Specification no. 26 53 508. In the manner described therein this noise pulse suppression circuit prevents noise pulses from being reproduced by keeping the amplitude level of the stereo multiplex signal just prior to each noise pulse constant during the occurrence of the noise pulse.
  • this noise pulse suppression circuit does however not prevent the occurrence of a noise pulse- dependent mono reproduction.
  • the noise pulses must also be eliminated in the control path which, in accordance with the invention, is effected by means of the last-mentioned bandpass filter.
  • the choice of the filter parameters of this bandpass filter is based on the recognition, that noise components which are the result of man made noise become manifest in the output signal of the level detector in a frequency range above 10 KHz.
  • amplitude variations of the FM-IF signal between approximately 1 KHz and 10 KHz are almost exclusively produced by multipath reception effects.
  • a preferred embodiment of an FM-receiver in accordance with the invention is characterized in that in the control signal generating circuit the level detector is part of a field strength detector and is connected in a wide-band mode to a first input of a differential stage, and that the multipath reception detector is connected to a second input of the differential stage, the differential stage being connected via a first delay circuit to the mono-stereo control circuit, this first delay circuit producing a continuously variable mono-stereo control signal having a rise time constant of at least 100 msec at a change-over to mono reproduction and a decay time constant of not more than 10 msec at a change to stereo reproduction.
  • a still further preferred embodiment of the FM-receiver in accordance with the invention is characterized by a continuous tone control, as well as by a second delay circuit arranged between the level detector and the continuous tone control for producing a continuously variable tone control signal having a rise time and a decay time constant of the order of magnitude of 1.5 sec. and 500 msec., respectively.
  • Fig. 1 shows an FM-receiver in accordance with the invention comprising an aerial A having connected thereo, in succession, an RF-input and tuning stage 1, an FM-IF portion 2, an FM-detector 3, an interference absorption circuit (IAC) functioning as a noise pulse suppressing circuit 4, a stereo decoder 5, left and right audio output stages 6, 7 and loudspeakers L and R.
  • IAC interference absorption circuit
  • a desired FM-aerial signal is selected and converted to a fixed FM-intermediate frequency (10.7 MHz) by means of the RF-input and tuning stage 1, is amplified and limited in the FM-IF portion and frequency-demodulated by the FM-detector 3.
  • the baseband modulation signal thus obtained is freed from noise pulses in the noise pulse suppression circuit 4 which is, for example, provided by the integrated circuit TDA 1001A and, in the event of a stereo multiplex signal is further decoded into left and right stereo signals which are reproduced by means of the loudspeakers L and R after having been amplified in the audio output stages 6 and 7.
  • the stereo decoder 5 of an FM-receiver in accordance with the invention is provided by an integrated circuit of the type TDA 1005A.
  • This integrated circuit also comprises a mono-stereo control circuit and a tone control circuit, both not shown, which effect in known manner a continuous mono-stereo change-over and a continuous tone control in the reproduction by means of a control signal applied to mono-stereo and tone control inputs 16 and 17, respectively.
  • an FM-receiver in accordance with the invention comprises a control signal generating circuit 8-15, which comprises an amplitude detector which functions as a level detector 8 and is connected to the FM-IF portion 2 and to which a non-limited FM-intermediate frequency signal is applied.
  • the time constant of the level detector 8 has been chosen sufficiently small ( ⁇ 0.1 msec.) to detect the spurious modulation-of the FM-intermediate frequency signal over a wide frequency range, for example from O to at least 10 KHz and preferably 100 KHz. Consequently, the output signal of the level detector 8 accurately indicates the field strength of the received signal and is applied as a wide-band signal to a first input 11 of a differential stage 13.
  • the output of the level detector 8 is also connected to a multipath receptinn detector 9, 10, which comprises a bandpass filter 9 and an amplitude detector 10 coupled thereto.
  • the spurious modulation signal thus selected is thereafter integrated in the amplitude detector 10, which in a practical embodiment had a time constant of approximately 500 msec.
  • the bandpass filter 9 has a 3 dB-passband range of not more than 10 KHz around a central frequency of the order of magnitude of 5 KHz and the amplitude detector 10 has a time constant of at least 50 msec.
  • the output signal of the amplitude detector 10 gives a rather accurate indication of the degree of a multipath reception in the received FM-signal, which is not or hardly affected by noise pulses.
  • This output signal is applied to a second input 12 of the differential stage 13 and subtracted therein from the above-mentioned signal at the first input 11.
  • the difference signal 6 thus obtained at the output of the differential stage 13 is used for both the mono-stereo control and the tone control of the stereo decoder which is provided by the integrated circuit (TDA 1005A).
  • An increase of this difference signal effects a delayed increase of the spatial sound impression and a likewise delayed increase of the audible frequency range and a decrease of the difference signal is substantially directly followed by a decrease of the spatial sound impression and followed after a delay by a decrease of the audible frequency range.
  • the signal delays required therefor are realised, in a manner still further to be described, by means of first and second delay circuits 14 and 15 arranged between the differential stage 13 and the mono-stereo control input 16 and the tone control input 17, respectively of the stereo decoder 5 which is provided by the integrated circuit (TDA 1005A). In the event of a variable receiving signal quality these signal delays enhance a spatial and a frequency-based stabilization of the sound impression, respectively.
  • Fig. 2 shows a practical embodiment of a control signal generating circuit 8-15 in which circuits whose functions correspond to those of the circuits shown in the preceding Figure have been given the same reference numerals.
  • the level detector 8 is realised by means of an integrated circuit of the type TEA 5560.
  • An output of the level detector 8 is connected to a non-inverting T&nput of a differential amplifier 18 via a first input 11 of differential stage 13 and a voltage divider 19, 20 and also to an inverting input of differential amplifier 18 via the multipath reception detector 9, 9', 10, 10', the second input 12 of the differential stage 13 and an input resistor 21.
  • An output of the differential amplifier 18 is connected to said inverting input via a feedback resistor 22.
  • the mul.tipath reception detector 9, 9', 10, 10' comprises an amplifier 9' arranged between the bandpass filter 9 and the amplitude detector 10, and a delay circuit 10' connected to the output of the amplitude detector 10.
  • the amplifier 9' provides in combination with the input resistor 21, the feedback resistor 22 and the voltage divider 19, 20 an adequate mutual amplitude match and difference formation of the multipath reception indication and the field strength indication.
  • This delay circuit 10' may if so desired be of the same construction as the first delay circuit 14 described hereafter and may optionally replace this first delay circuit 14 or be replaced by it.
  • the output signal of the differential amplifier 18 is applied to the first delay circuit 14 to be submitted therein to a delay in the event of an increasing amplitude.
  • the first delay circuit 14 comprises a comparison circuit 25, which is connected to the output of the differential amplifier 13 via a series arrangement of a resistor 23 and a diode D 1 .
  • the cathode of the diode D 1 is connected to ground via a resistor 24 and is also connected to an inverting input of the operational amplifier 29 of the comparison circuit 25.
  • An output of the operational amplifier 29 is connected via a resistor 30 to the base of a transistor 31, whose emitter is connected to ground and whose collector forms the output of the comparison circuit 25.
  • This collector output is fed-back to a non-inverting input of the operational amplifier 29 and is also connected to the cathode of a diode D 2 via a grounded capacitor 26.
  • the anode of this diode D 2 is connected via the mono-stereo control input 16 to the integrated circuit of the type TDA 1005A, which, in addition to the stereo decoder also comprises a voltage source 28, which is connected to the mono-stereo control input 16 via the resistor 27.
  • This voltage source 28 supplies a voltage of approximately 1.4 V on receipt of FM-stereo signals and a voltage of 0 V on receipt of FM-mono signals.
  • the capacitor 26 is slowly charged from the voltage source 28 via the resistor 27 and the diode D 2 with an RC-time constant determined by the resistor 26, the diode resistance of D 2 and the capacitance of the capacitor 26.
  • This what is commonly referred to as the rise time constant thus determines the rate of increase of the mono-stereo control signal at control input 26 and, for an adequate operation, should amount- to at least 100 msec.
  • a decrease of the output voltage of the differential stage 13 results in the voltage across the capacitor 26, that is to say the voltage at the non-inverting input of the operational amplifier 29 becoming larger than the voltage at the inverting input.
  • the output voltage of the operational amplifier 29 becomes positive and, via the resistor 30, makes the transistor 31 conductive, which shortcircuits the voltage across the capacitor 26.
  • a decrease of the output voltage of the differential stage 13 is almost immediately followed by a decrease of the mono-stereo control signal.
  • the time constant being commonly referred to as the decay time constant, and being determined by the transistor 31 and the capacitor 26 is substantially zero and.must not be more than 10 msec. for adequate operation.
  • the delay circuit 10' may optionally be omitted. It is alternatively possible to omit the signal delays in the first delay circuit 14 when the delay circuit 10' is used, by omitting the comparison circuit 25 and the capacitor 26.
  • the output signal of the differential stage 13 is also applied to the second delay circuit 15 to be submitted therein to a delay, both when the ' amplitude increases or decreases.
  • the second delay circuit 15 comprises a grounded capacitor 33, one side of which being connected to the differential stage 13 via a series arrangement of a diode D 3 and a resistor 32 and the other side being connected via a diode D 4 to the tapping point of a voltage divider 34, 35 arranged between a supply voltage and ground.
  • the diodes D 3 and D 4 have been chosen such that a discharge path of the capacitor 33 is formed by the diode D 3 , the resistor 32 and the output impedance of the differential stage 13 and that a charging path is formed by the resistor 34 of the voltage divider 34, 35 and the diode D 4 .
  • the tapping point of the voltage divider 34, 35 is also connected via a capacitor 36 to the tone control input 17, to which a voltage source 38 applies a stereo sum signal (L+R)-depending signal voltage via a resistor 37.
  • a capacitor 36 forms a variable tone filter at the tone control input 17, which variably filters the stereo sum signal L+R supplied by the voltage source 38.
  • the capacitor 33 will be discharged via the diode D 3 and the resistor 32. As a result thereof the capacitor voltage becomes less than the voltage at said tapping point, so that the diode D 4 starts conducting.
  • the stereo sum signal (L+R) applied to the tone control input 17 is short-circuited frequency- dependently via the capacitor 36, the diode resistance of the diode D 4 which resistance depends on the degree of conduction, and the capacitor 33.
  • This tone control follows a decrease of the output signal of the differential stage with a delay having an RC time constant or so-called decay time constant which is determined by the capacitance of the capacitor 33 and the resistance value of the diode D 31 the resistor 32 and the output impedance of the differential stage 13.
  • the diode D 3 is cut-off and the capacitor 33 is charged with an RC time constant or so-called rise time constant determined by the capacitance of the capacitor 33 and the resistance values of the diode resistance of D 4 and the resistor 34.
  • the diode resistance of D 4 then gradually increases as does also, frequency- wise, the cross-over point in the frequency response characteristic which is realised by the capacitors 33 and 36 and the diode D 4 .
  • the tone congrol then follows a decrease of the output signal of the differential stage 13 with a delay equal to the last-mentioned time constant.
  • the resistors had the following values:

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Stereo-Broadcasting Methods (AREA)
  • Noise Elimination (AREA)
  • Circuits Of Receivers In General (AREA)
EP83201127A 1982-08-31 1983-07-29 FM-Stereoempfänger Expired EP0103917B1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
NL8203384A NL8203384A (nl) 1982-08-31 1982-08-31 Fm-stereo-ontvanger.
NL8203384 1982-08-31

Publications (2)

Publication Number Publication Date
EP0103917A1 true EP0103917A1 (de) 1984-03-28
EP0103917B1 EP0103917B1 (de) 1986-10-29

Family

ID=19840203

Family Applications (1)

Application Number Title Priority Date Filing Date
EP83201127A Expired EP0103917B1 (de) 1982-08-31 1983-07-29 FM-Stereoempfänger

Country Status (7)

Country Link
US (1) US4491957A (de)
EP (1) EP0103917B1 (de)
JP (1) JPS5958930A (de)
DE (1) DE3367312D1 (de)
HK (1) HK39787A (de)
NL (1) NL8203384A (de)
SG (1) SG20187G (de)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2578702A1 (fr) * 1985-03-06 1986-09-12 Clarion Co Ltd Circuit generateur de tension de commande pour actionner un circuit reducteur de bruit dans un appareil recepteur stereo a modulation de frequence
EP0217475A1 (de) * 1985-10-02 1987-04-08 Koninklijke Philips Electronics N.V. Empfänger mit Detektor für Mehrwegübertragung
EP0351916A2 (de) * 1988-07-22 1990-01-24 Philips Patentverwaltung GmbH Stereo-Empfangsschaltung
DE19542737A1 (de) * 1995-11-16 1997-05-22 Bayerische Motoren Werke Ag Schaltanordnung für mobile Rundfunkempfänger
GB2370948A (en) * 2000-11-09 2002-07-10 Mitsubishi Electric Corp Multipath and pulse noise removal for an FM receiver

Families Citing this family (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4574390A (en) * 1983-03-26 1986-03-04 Victor Company Of Japan, Limited Noise reduction for stereophonic FM signals by high-speed sampling and linear interpolation
JPS6237456U (de) * 1985-08-23 1987-03-05
US5204904A (en) * 1986-12-01 1993-04-20 Carver Corporation Apparatus for receiving and processing frequency modulated electromagnetic signals
US4833715A (en) * 1987-03-06 1989-05-23 Alps Electric Co., Ltd. FM stereo receiver
US4847903A (en) * 1987-05-22 1989-07-11 Recoton Corporation Wireless remote speaker system
US5530737A (en) * 1993-03-22 1996-06-25 Phonex Corporation Secure access telephone extension system and method
DE19542738A1 (de) * 1995-11-16 1997-05-22 Bayerische Motoren Werke Ag Schaltanordnung für mobile Rundfunkempfänger
JP2004128930A (ja) * 2002-10-03 2004-04-22 Toyota Industries Corp Ｆｍ受信機、ｆｍ受信機のノイズ除去装置及びノイズ除去方法
KR100504141B1 (ko) * 2003-01-22 2005-07-27 삼성전자주식회사 휴대용 단말기에서 삼차원 서라운드 효과를 가지는 장치및 방법
JP5000936B2 (ja) * 2006-06-27 2012-08-15 オンセミコンダクター・トレーディング・リミテッド マルチパスノイズ検出装置及びｆｍ受信装置
DE112009000388B4 (de) * 2008-03-11 2012-12-20 Mitsubishi Electric Corporation Funkempfänger
EP2982061B1 (de) 2013-04-04 2016-11-02 Koninklijke Philips N.V. Empfänger, sender, sender-empfänger-modul für eine körpergekoppelte kommunikationsvorrichtung, ein körpergekoppeltes kommunikationssystem und verfahren zum aufwecken eines körpergekoppelten empfängers einer körpergekoppelten kommunikationsvorrichtung

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3034937A1 (de) * 1979-09-17 1981-04-09 Nissan Motor Co., Ltd., Yokohama, Kanagawa Schaltung zur automatischen rauschunterdrueckung in einem fm-empfaenger
EP0030874A1 (de) * 1979-12-17 1981-06-24 Sanyo Electric Co., Ltd. Schaltung zur Verzerrungsminderung für einen FM-Empfänger
DE3131292A1 (de) * 1980-08-07 1982-05-27 Clarion Co., Ltd., Tokyo Fm-rauschunterdrueckungsschaltung

Family Cites Families (9)

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NL145420B (nl) * 1969-10-25 1975-03-17 Philips Nv Schakeling voor het onderdrukken van storingen in een fm radio-ontvanger.
JPS5750097B2 (de) * 1973-06-06 1982-10-26
US3999132A (en) * 1975-10-31 1976-12-21 Motorola, Inc. Stereo inhibit circuit
IT1052399B (it) * 1975-11-25 1981-06-20 Autovox Spa Circuito elettronico per la soppressione dei disturbi nei radioricevitori
SE432683B (sv) * 1977-06-17 1984-04-09 Sharp Kk Storningsreducerande krets for en fm-stereomottagare
DE2929647C2 (de) * 1979-07-21 1990-09-13 Blaupunkt-Werke Gmbh, 3200 Hildesheim UKW-Stereo-Autoempfänger
JPS56169439A (en) * 1980-06-02 1981-12-26 Pioneer Electronic Corp Noise suppressing circuit for fm receiver
JPS57121345A (en) * 1981-01-20 1982-07-28 Sanyo Electric Co Ltd Pulse noise eliminating circuit
US4408098A (en) * 1981-06-18 1983-10-04 U.S. Philips Corporation Receiver with field-strength dependent noise reduction control

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3034937A1 (de) * 1979-09-17 1981-04-09 Nissan Motor Co., Ltd., Yokohama, Kanagawa Schaltung zur automatischen rauschunterdrueckung in einem fm-empfaenger
EP0030874A1 (de) * 1979-12-17 1981-06-24 Sanyo Electric Co., Ltd. Schaltung zur Verzerrungsminderung für einen FM-Empfänger
DE3131292A1 (de) * 1980-08-07 1982-05-27 Clarion Co., Ltd., Tokyo Fm-rauschunterdrueckungsschaltung

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2578702A1 (fr) * 1985-03-06 1986-09-12 Clarion Co Ltd Circuit generateur de tension de commande pour actionner un circuit reducteur de bruit dans un appareil recepteur stereo a modulation de frequence
EP0217475A1 (de) * 1985-10-02 1987-04-08 Koninklijke Philips Electronics N.V. Empfänger mit Detektor für Mehrwegübertragung
EP0351916A2 (de) * 1988-07-22 1990-01-24 Philips Patentverwaltung GmbH Stereo-Empfangsschaltung
EP0351916A3 (de) * 1988-07-22 1991-08-28 Philips Patentverwaltung GmbH Stereo-Empfangsschaltung
DE19542737A1 (de) * 1995-11-16 1997-05-22 Bayerische Motoren Werke Ag Schaltanordnung für mobile Rundfunkempfänger
US5771293A (en) * 1995-11-16 1998-06-23 Bayerische Motoren Werke Aktiengesellschaft Switching arrangement for mobile radio receivers
GB2370948A (en) * 2000-11-09 2002-07-10 Mitsubishi Electric Corp Multipath and pulse noise removal for an FM receiver
GB2370948B (en) * 2000-11-09 2004-09-15 Mitsubishi Electric Corp Noise removal apparatus and an FM receiver
US6993309B2 (en) 2000-11-09 2006-01-31 Mitsubishi Denki Kabushiki Kaisha Noise removal apparatus and an FM receiver
DE10154973B4 (de) * 2000-11-09 2010-07-29 Mitsubishi Denki K.K. Rauschentfernungsvorrichtung und FM-Empfänger

Also Published As

Publication number Publication date
NL8203384A (nl) 1984-03-16
SG20187G (en) 1990-01-26
JPH0527290B2 (de) 1993-04-20
US4491957A (en) 1985-01-01
HK39787A (en) 1987-05-29
JPS5958930A (ja) 1984-04-04
DE3367312D1 (en) 1986-12-04
EP0103917B1 (de) 1986-10-29

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